19951621 has 4 divisors (see below), whose sum is σ = 20490892. Its totient is φ = 19412352.

The previous prime is 19951609. The next prime is 19951627. The reversal of 19951621 is 12615991.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13060996 + 6890625 = 3614^2 + 2625^2 .

It is a cyclic number.

It is not a de Polignac number, because 19951621 - 2⁷ = 19951493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19951627) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 269580 + ... + 269653.

It is an arithmetic number, because the mean of its divisors is an integer number (5122723).

Almost surely, 2^19951621 is an apocalyptic number.

It is an amenable number.

19951621 is a deficient number, since it is larger than the sum of its proper divisors (539271).

19951621 is an equidigital number, since it uses as much as digits as its factorization.

19951621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 539270.

The product of its digits is 4860, while the sum is 34.

The square root of 19951621 is about 4466.7237434164. The cubic root of 19951621 is about 271.2227169286. Note that the first 3 decimals are identical.

The spelling of 19951621 in words is "nineteen million, nine hundred fifty-one thousand, six hundred twenty-one".